1. Field of the Invention
The present invention relates to intelligent movable robots which are freely movable along unlimited paths in operational areas. In particular, the present invention relates to a movable robot which is freely movable along an unlimited path in an operational area by using a rechargeable battery and without being restricted by an external power-source cable.
More particularly, the present invention relates to a method of controlling an electrical power for a movable robot which is freely movable along an unlimited path in an operational area so that the movable robot does not operate uncontrolled or tumble even when the remaining power of the battery becomes low at a position in the operational area.
2. Description of the Related Art
A mechanical apparatus, which performs movements similar to those of a human being by using electrical and/or magnetic effects, is called a xe2x80x9crobotxe2x80x9d. The term xe2x80x9crobotxe2x80x9d is said to be originated from a Slavic word xe2x80x9crobotaxe2x80x9d which means a slave-machine. In Japan, the robots began to be widely used in the late 1960s, most of which were industrial robots, such as manipulators and transfer robots, serving for automated and unmanned manufacturing operations in factories.
A stationary robot, such as an arm-type robot which is fixed so as to be used in a particular place, is operated only in a limited small operational area such as for assembly and selection of component parts. On the other hand, a movable type robot can operate in an unlimited operational area, is movable along a predetermined or unlimited path, and performs a predetermined or any operation on behalf of human beings, so as to provide various wide services which replace for those offered by live bodies including human beings, dogs, and others. Particularly, a movable legged robot is superior to the other movable type robots, in that a flexible walking or traveling motion, such as ascending and descending steps and chairs and climbing over barriers, is possible regardless of the condition of walking or traveling area of the legged robot, although attitude control and movement control are difficult because the legged robot is instable compared with a crawler-type robot or a robot having tires.
Recently, studies have been advanced concerning legged robots including a pet-type robot which copies the physical mechanism and motions of four-legged animals, such as cats and dogs, and a xe2x80x9cman-shapedxe2x80x9d or xe2x80x9cman-typexe2x80x9d (humanoid) robot which is designed by using the physical mechanism and motions of two-legged lives, such as human beings, as models, and practical applications of these robots are more expected.
Most of the working and residential areas of the human beings are formed in accordance with the physical mechanism and operation patterns of the human beings which move by using two legs. In the residential area of the human beings, there are too many obstacles for existing mechanical systems which use wheels and the like as driving mechanisms for moving. The mechanical system, that is, a robot is preferably formed to have substantially the same range of movement as that of the human beings so that the robot can assist or substitute for the human beings in their operations and further penetrate into the human life. This is the reason why the practical use of legged robots is looked forward. It is indispensable for the robots to have shapes of the human beings so that the robots can be adapted to the human life.
The man-shaped robots perform various operations of industrial production activities and the like for the human beings, for example, maintenance operations for nuclear and thermal power generation plants and petrochemical plants, transfer and assembly operations for component parts in manufacturing plants, cleaning of high-rise buildings, and rescue works in sites of fires which are operations dangerous or difficult to the human beings to perform.
The man-shaped robots may be also used in a xe2x80x9csymbiotic relationshipxe2x80x9d and for xe2x80x9centertainmentxe2x80x9d. In these types of use, the robots are characterized more in living together with the human beings than in assistance of the human life.
The robots described above are electric-motor-driven mechanical devices; therefore, the electrical supply to the devices is indispensable.
In a stationary robot such as an arm-type robot which is fixed so as to be used in a particular place, or in a movable robot of which the action radius or operation patterns are limited, the power can be supplied from a commercial AC power source via a power cable.
On the other hand, in an independent type robot which freely moves, the power supply from the commercial AC power source is not possible because the action radius of the robot is restricted by the power cable. Therefore, the movable robot is independently driven by a rechargeable battery. The battery-driven movable robot is independently movable in a residential area of the human beings or in various operational areas without considering physical restriction of the position of power sockets and the length of a power cable.
For example, in a mechanical device such as the man-shaped robot, which has a multidegree of freedom, that is, numbers of joint-actuators, of which the power consumption is great, a high-capacity and high-output battery is required for supplying an inrush current when starting actuators. Particularly, strong actuators are required for leg members, thereby consuming large power. Therefore, the weight of a battery increases so as to occupy 10 to 20% of the total weight of the robot, and, in turn, the increase of the weight causes greater consumption of the power. However, the robot is still preferably driven by a battery in order to be free from interference of legs of the robot with the power cable and restriction of the action radius due to a limited length of the power cable and to maintain the freedom of action of the robot.
A difficult point of a battery-driven mechanical device is a battery-charge operation. Particularly, although the movable robot is used as an automatic device or unmanned machine, charging operation cannot be automatically performed. The operation of battery replacement and connection to a power source for charging is a laborious work for users.
For example, when the man-shaped robot must suspend its operations so as to manually perform charging of the battery every time when the capacity of the battery decreases while the robot is assisting or substituting for the human beings in various occasions happening in a residential area, it cannot be said that the robot performs its roll as a partner of the human beings, but it must be said that the human beings serve as assistants to the robot.
In order to automate the battery-charging operation for movable robots, so-called a xe2x80x9ccharging stationxe2x80x9d is used. The charging station is an exclusive space for charging batteries of the movable robots.
A method of charging a battery of a battery-driven robot at a charging station, which freely moves along an unlimited path in an operational area, is disclosed in, for example, Japanese Patent Application No. 11-308224, the right of which has been transferred to the assignee of the present invention, in which visible identification data are disposed in a predetermined position of the charging station, and a legged movable robot is provided with an imaging unit, a computing unit for computing the distance and direction of the charging station from the movable robot in accordance with a captured image, and a searching unit for making the movable robot to search the charging station in accordance with the result of computation by the computing unit. The legged movable robot can search the charging station by chasing the visible identification data by a camera, thereby automating the charging operation.
Another method of charging a battery of a movable robot at the charging station is disclosed in, for example, Japanese Patent Application No. 11-366651, the right of which has been transferred to the assignee of the present invention, in which a legged movable robot independently determines the time at which the battery-charging is required, and drops in the charging station for charging, whereby assistance of a user or the like is not necessary. The user becomes free from a laborious charging operation, and it is not necessary for the user to consider the time to charge a battery. In a match game between legged robots, the spectators can enjoy the game (for example, soccer) without loosing continuity and reality of the game.
However, an intelligent robot which independently moves along an unlimited path in an operational area does not always happen to be close to a charging station when the battery should be charged.
When a full operation of the robot continues when the remaining capacity is low, discharging of the battery is accelerated, and there is a risk in that the battery is completely discharged before the robot reaches the charging station.
When an unplanned operation-pattern is performed at the time when the power is cut off, the robot tumbles down to a floor while being in an unnatural position. In this case, there is a risk of seriously damaging the robot or an object with which the tumbling robot collides, an economical effect of repairs being serious. Particularly, a man-shaped legged robot is tall and has its center of gravity at an elevated level; therefore, damages due to the tumble caused by unexpected interruption of power becomes more serious.
Accordingly, it is an object of the present invention to provide an intelligent robot freely movable along an unlimited path in an operational area.
It is another object of the present invention to provide a superior movable robot which is freely movable by using a rechargeable battery along an unlimited path in an operational area without being restricted by an external power cable.
It is still another object of the present invention to provide a superior technology of power control of a movable robot which is freely movable along an unlimited path in an operational area.
It is a further object of the present invention to provide a superior technology of power control of a movable robot, in which the movable robot does not operate in an unplanned state nor tumble due to interruption of power supply.
To these ends, according to an aspect of the present invention, a battery-driven legged robot, which comprises at least one movable leg unit and at least one driving member including the driving member for driving a trunk, comprises a control unit for outputting a control signal for instructing driving of the driving member; a power-control unit for monitoring the state of a battery; and a power supply-block unit for supplying and blocking driving power to the driving member in accordance with the state of the battery monitored by the power-control unit.
The control unit may block the output of the control signal to the driving member to which the driving power has been blocked.
The battery-driven legged robot may further comprise at least one device of an attitude sensor, an image input device, and a sound input-output device. The power-control unit may block the driving power to the at least one device of the attitude sensor, the image input device, and the sound input-output device when power of the battery decreases below a predetermined value, thereby reducing power consumption.
The battery-driven legged robot may further comprise a head unit. The power-control unit may block the driving power to the head unit before blocking the driving power to the movable leg unit, when the power of the battery decreases below a predetermined value, whereby a motion using the movable leg unit can be continued while reducing the power consumption.
The battery-driven legged robot may further comprise an arm unit. The power-control unit may block the driving power to the arm unit before blocking the driving power to the movable leg unit, when the power of the battery decreases below a predetermined value, whereby the motion using the movable leg unit can be continued while reducing the power consumption.
The battery-driven legged robot may further comprise a trunk unit. The power-control unit may block the driving power to the trunk unit before blocking the driving power to the movable leg unit, when the power of the battery decreases below a predetermined value, whereby the motion using the movable leg unit can be continued while reducing the power consumption.
The control unit may provide an instruction to change a control parameter for the at least one driving member when the control unit receives information from the power-control unit that the power of the battery has decreased below a predetermined value.
The control unit may change a controlled motion set for the at least one driving member when the control unit receives information from the power-control unit that the power of the battery has decreased below a predetermined value.
The above-described change of the controlled motion may include a change of a target position of movement set for the driving member, suspension of movement of the at least one driving member, a motion for connecting to an external power supply device, and a movement to a stable position in which the center of gravity of the legged robot is disposed sufficiently low and suspension of the supply of the driving power to substantially all the driving members when the legged robot is in the stable position.
When the battery-driven legged robot comprises the head unit, the arm unit, and the trunk unit, the power-control unit may block, in the switching step, the driving power to the head unit, the arm unit, and the trunk unit, one after another, when the power of the battery decreases below a predetermined value, whereby the motion using the movable leg unit can be continued while reducing the power consumption.
According to another aspect of the present invention, a method of controlling a battery-driven legged robot is provided, the legged robot comprising at least one movable leg unit and at least one driving member including the driving member for driving a trunk. The method of controlling a battery-driven legged robot comprises the steps of monitoring the state of a battery; and switching between supply and blocking of driving power to the at least one driving member in accordance with the state of the battery monitored in the monitoring step.
The method of controlling a battery-driven legged robot may further comprise the step of blocking an output of a control signal to the driving member to which the driving power has been blocked.
In the method of controlling a battery-driven legged robot, the legged robot may further comprise at least one device of an attitude sensor, an image input device, and a sound input-output device. In the switching step, the driving power to the at least one device of the attitude sensor, the image input device, and the sound input-output device may be blocked when determined in the monitoring step that power of the battery has decreased below a predetermined value, thereby reducing power consumption.
In the method of controlling a battery-driven legged robot, the legged robot may further comprise a head unit. In the switching step, the driving power to the head unit may be blocked before blocking the driving power to the leg unit, when determined in the monitoring step that the power of the battery has decreased below a predetermined value, whereby a motion using the movable leg unit can be continued while reducing the power consumption.
In the method of controlling a battery-driven legged robot, the legged robot may further comprise an arm unit. In the switching step, the driving power to the arm unit may be blocked before blocking the driving power to the leg unit, when determined in the monitoring step that the power of the battery has decreased below a predetermined value, whereby the motion using the movable leg unit can be continued while reducing the power consumption.
In the method of controlling a battery-driven legged robot, the legged robot may further comprise a trunk unit. In the switching step, the driving power to the trunk unit may be blocked before blocking the driving power to the leg unit, when determined in the monitoring step that the power of the battery has decreased below a predetermined value, whereby the motion using the movable leg unit can be continued while reducing the power consumption.
The method of controlling a battery-driven legged robot may further comprise the step of providing an instruction to change a control parameter for the at least one driving member when determined in the monitoring step that the power of the battery has decreased below a predetermined value.
The method of controlling a battery-driven legged robot may further comprise the step of changing a controlled motion set for the at least one driving member when determined in the monitoring step that the power of the battery has decreased below a predetermined value.
The above-described change of the controlled motion may include a change of a target position of movement set for the driving member, suspension of movement of the at least one driving member, a motion for connecting to an external power supply device, and a movement to a stable position in which the center of gravity of the legged robot is disposed sufficiently low and suspension of the supply of the driving power to substantially all the driving members when the legged robot is in the stable position.
In the method of controlling a battery-driven legged robot, when the legged robot comprises the head unit, the arm unit, and the trunk unit, the driving power to the head unit, the arm unit, and the trunk unit may be blocked, one after another, in the switching step, when the power of the battery decreases below a predetermined value.
According to the present invention, when the remaining capacity of a battery of the robot comes to a low level at a position in an operational area, power consumption can be reduced, thereby extending the life of the battery, by changing control parameters used by actuators and successively suspending operations of driving members of which the suspension of operations does not significantly affect the motion using leg units.
Therefore, the robot can operate for a longer time, and energy which is required for the motion for connection to a charging station or an external power supply device can be maintained.
According to the present invention, when the remaining capacity of a battery of the robot comes to a low level at a position in an operational area, the robot changes its position to that in which the robot is, for example, sitting down, lying on its face, or lying on its back, so that it is not necessary for the driving members to drive (to consume power for) the leg unit and the like for maintaining the position of the robot, and the center of gravity of the robot is sufficiently low, whereby a risk of damaging the robot and an object with which the robot collides by tumbling can be avoided.
Further objects, features, and advantages of the present invention will become apparent from the following detailed description of the embodiments according to the present invention with reference to the attached drawings.